pathology
Last reviewed 10/2022
In TTP there is aggregation of platelets that obstruct reversibly the arterioles and capillaries of various organs resulting in fluctuating ischaemia (and sometimes infarction).
Features include:
- brain is involved in 50-71% of cases
- early capillary and arteriolar microthrombi in TTP consist almost exclusively of microthrombi without perivascular inflammation
- TTP is associated with excessive release of ULvWF multimeric forms from systemic endothelial cells. If these endothelial cells are perturbed transiently then a single-episode of TTP occurs; if perturbed periodically then intermittent TTP occurs
- immunohistochemical studies in thrombi in TTP have revealed:
- an abundance of von Willebrand factor
- little fibrinogen/fibrin
- both are opposite findings to those seen in thrombotic lesions in DIC